New maps show city’s biggest tsunami risks

RISK ZONES: Red is a tsunami less than a metre, orange up to 3m, and yellow 3m or more. Water height doubles on land.

THE sea would lap round the Beehive, the airport would be submerged and the Cake Tin surrounded by water.

These are some of the devastating effects Wellington would suffer in the kind of tsunami that hits here once every 500 years, according to new maps produced by the Greater Wellington Regional Council.

The “wall of water” – higher than three metres – would flood Kilbirnie, Miramar, Island Bay and Petone and other parts of the Hutt, and would cause significant damage as the initial wave hit and then drained away.

An even bigger wave, a monster higher than five metres, can be expected once every 2500 years, in which case even the Basin Reserve would have a sticky wicket.

Central Miramar is “like a giant teacup” and water would drain into other parts of the suburb after the initial strike.

The oil storage tanks near Petone would be wiped out and a really big tsunami would charge right up the Hutt River.

The maps – drawn up by Greater Wellington Regional Council natural hazards analyst Iain Dawe and published for the first time here on NewsWire – are being used in preparations for a Wellington City Council campaign early next year to raise awareness about tsunami risk.

They show three danger zones – immediate shoreline (red), areas that would be flooded in a one-in-500-year tsunami (orange), and – higher up – those at risk in the 2500-year event (yellow).

On average, a tsunami larger than one metre and as high as three metres hits the Wellington region once every 84 years, says Civil Defence Management Group manager Rian van Schalkwyk (pictured left).

He says Wellington could be hit by a tsunami in one of two ways – either from a local earthquake or from an earthquake in another part of the Pacific region, most likely near South America.

A tsunami created from a local earthquake would be far more dangerous as it would likely be bigger and there would be a lot less warning time.

Earthquakes that cause tsunamis do not occur on a regular time frame and the 84 and 500 year numbers are just the average time between significant events.

The last major tsunami here was caused by an 8.1 to 8.3 magnitude earthquake along the Wairarapa fault line in 1855, he told a Wellington Region Civil Defence Management Group meeting this month.

The tsunami caused 10 metre high waves in Palliser Bay and three to four metre waves in Wellington Harbour.

A large tsunami would move back and forth in Wellington Harbour, causing damage for about 18 hours,

He told the meeting – which included some of the region’s mayors – that the waves can be much higher on land than at sea. The recent tsunami in Samoa was three metres high at sea and six to eight metres on land.

TSUNAMI POWER: Before and after shots showing the Boxing Day tsunami overwhelming a tower in Indonesia. IMAGES: Greater Wellington Regional Council presentation.

Wellington City Council has already purchased 60,000 leaflets showing information about what to do in the case of a tsunami and how to prepare for one.

The council’s emergency preparedness manager, Fred Mecoy, says these will be released as part of a wider campaign, which will include awareness presentations in areas likely to be affected.

He hopes the recent tsunami in Samoa will mean people are more likely to listen to the campaign.

The maps below show other areas most at risk from different-sized tsunami:

The red areas along the coast (the beach area) are the immediate evacuation zone and would be inundated by a tsunami as small as one metre.

Civil Defence would assist in the evacuation of those in the orange areas, which would be hit by a larger one-in-500-year tsunami of about three to four metres.

A one-in-2500-year tsunami of above five metres would flood the areas coloured yellow, labelled as the self-evacuation zone because emergency management would not have the capacity to evacuate such a large area.

Vaughan Elder is an aspiring political journalist. I came up to Wellington after living in Dunedin all my life. I have a degree in politcal science and would love to be a political reporter.Email this author | All posts by Vaughan Elder

Hi guys, I am very concerned that schools in the Otahuhu, Mangere and Papakura areas do not have any idea of the tsunami risk. Would it be possible to get a map done for Auckland so that our schools can start to organise evacuation or safety strategies …